The present invention relates to a mask used to allow formation of a desired pattern as a projection on a semiconductor wafer or the like, and particularly to a method for correcting white defects in a stencil mask of an electron beam system.
Silicon stencil white defect correction (repair processing for missing locations) has been performed in the related art with deposition of carbon or the like using a focused ion beam device, namely by injecting an aromatic gas such as phenanthrene from a gas gun onto a defective region, and at the same time irradiating an ion beam to the defective region, and performing carbon deposition to bury the defects. FIG. 5 shows a design pattern opening 3 formed in a thin film 2 with a stencil for electron beam processing, and has a basic structure of lattice shaped struts 4 forming a lining so as to impart mechanical strength to a stencil, being a thin film. However, as shown in FIG. 3, in the event that repair processing is carried out as processing to construct a bridge across a groove shaped opening 31, the related art method, as shown by the chain line in the center of the drawing, is implemented by making all defective regions spanning the two sides of the opening ion beam irradiation regions SE, and subjecting these regions to deposition, and so initially, in order to avoid a foundation for attaching carbon at the groove section, a deposition layer is not formed. Carbon attachment commences from an end section, attachment gradually advances on a carbon deposition layer where there is attachment, and the deposition layer is grown overlapping advancement in the thickness direction and the central direction. This aspect is shown in FIGS. 4A-4B. FIG. 4B is a view looking from above, and a deposition layer D is formed as a bridge across the groove opening 31, but in the side cross sectional view of FIG. 4A, the shape of the deposition layer D appears as a plurality of chronologically deposited layers. The lower layer D1 in the drawing is an initial processing layer, and the upper layers are deposited as processing time elapses, in the order (D2 greater than D3 greater than D4 greater than D5 greater than D6). At a point in time where the central sections join, the deposition layer D is formed thin at the central portion, and thick at the two end section. As is clear from this, there is a problem with the bridge film pattern formation method of the related art in that if thickness at the central section is to be guaranteed, the thickness at both end sections must be even thicker. In semiconductor lithography using photo etching, there is a light wavelength limit, and with the latest semiconductor processes capable of achieving ultra-high density, projection electron beam lithography is suitable. In the case of this projection electron beam lithography, it is necessary to obtain a scattering power of electrons by a silicon thin film, being a stencil, in a fixed range. Also, if the bridge becomes long, it is extremely difficult with deposition of the related art, and even if it is possible to form a bridge, at the point in time when the central sections join, the thickness at the two end sections is extremely large, and because of the difference in thickness, transmission and diffusion of electrons becomes non-uniform, and this is not suitable for a stencil.
The purpose of the present invention is to provide a correction method, in correction of white defects of a silicon stencil by deposition using a focused ion beam, where there is no difference in thickness between a deposition layer formed in defect end sections and a deposition layer formed at tip sections, realizing correction of defects where sections randomly become insufficiently thick, and to provide a correction method capable of forming a long bridge.
When forming a beam shaped body by deposition using a focused ion beam device on the end of a sample, the present invention adopts a beam shaped film pattern formation method for subjecting an irradiation region of an ion beam to deposition narrowly limited to a strip shape from ends of the sample, and sequentially shifting the irradiation region in a tip end direction to cause formation of a beam shaped body by growth of thin deposition layers, and causing formation of a deposition film of desired thickness on the thin deposition layers on the beam shaped body.